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On Tuesday, authorities dropped charges against another Mississippi man

The FBI said letters sent to Obama and two others tested positive for the toxin ricin

A Tupelo, Mississippi, man has been charged with possession and use of a biological agent as a weapon in connection with an investigation into ricin-tainted letters sent to President Barack Obama and others, federal authorities said Saturday.

The federal charges against James Everett Dutschke come days after prosecutors dropped charges against Paul Kevin Curtis in the same case amid Curtis' claims he was framed.

Dutschke, 41, is expected to appear in U.S. District Court in Oxford on Monday before Magistrate Judge S. Allan Alexander, according to a statement released by the U.S. attorney in the Northern District of Mississippi.

Dutschke was arrested without incident at his home early Saturday, FBI spokeswoman Deborah Madden said. Earlier this week, agents searched Dutschke's residence and former martial arts studio, though it's not clear what they found.

The arrest of Dutschke is the latest twist in a bizarre case that began earlier this month when federal investigators arrested Curtis, an Elvis impersonator from Corinth, Mississippi, for allegedly sending letters containing ricin, a deadly toxin, to Obama, Sen. Roger Wicker, R-Mississippi; and Sadie Holland, a judge in Lee County.

The letters touched off anxieties in Washington and elsewhere in the wake of the Boston Marathon bombings. Authorities later said the Boston bombings and the ricin-tainted letters were unrelated.

The revelation of the ricin-laden letters recalled the fear that gripped the country in the days following the September 11, 2001, terror attacks when anthrax-laced letters were sent to U.S. senators and journalists.

Prosecutors on Tuesday dropped the charges against Curtis after his attorney, Christi McCoy, told authorities that she believed her client was framed, possibly by Dutschke.

As Curtis, 45, walked out of jail, FBI agents were searching Dutschke's home and the studio where he practiced martial arts.

At the time, Dutschke told CNN affiliate WMC-TV that he agreed to the FBI search "to help clear my name."

"I had absolutely nothing to do with those letters," he said.

'I am KC'

The letters read, in part: "To see a wrong and not expose it, is to become a silent partner to its continuance."

They were signed "I am KC and I approve this message," a source told CNN.

Each letter had a Memphis, Tennessee, postmark and no return address.

Curtis, a self-styled activist known as Kevin Curtis, has used similar signoffs on letters and social media posts, his attorney said.

"I do believe that someone who was familiar and is familiar with Kevin just simply took his personal information and did this to him," attorney McCoy told CNN.

Curtis told CNN that he didn't even know what ricin was until he got out of jail and looked it up on the Internet.

When police stormed his home and arrested him last week, Curtis said an investigator asked him about ricin, and Curtis said he responded, "Well, I don't eat rice, and I don't have any rice in the house."

Online feud

Dutschke's attorney, Lori Basham, has said her client used to work for Curtis' brother, but the two have had no contact since 2010. Basham declined to comment on Dutschke's arrest Saturday.

The relationship between the two men is at best hazy, with each publicly accusing the other of bad behavior.

Curtis has said that while Dutschke worked for his brother, the two talked about collaborating on the publication of a book, but later had a falling out.

He has accused Dutschke of stalking him online, a claim the former taekwondo instructor has denied.

Dutschke told reporters this week that he did not know Curtis well.

"He's just a little nutty. I don't have a relationship with him," he said.

"I've met him two times in person, and then there was a third time we sent e-mails back and forth."

In the e-mail exchange, according to Dutschke, he accused Curtis of posting a fake membership certificate for MENSA, the high-IQ organization. Curtis acknowledged that he posted a fake certificate, but said he did it to catch Dutschke stalking him online.

Ties to letters?

Authorities have not said how they linked the letters to Dutschke, who appears to have personal ties to at least two of the three people who were sent letters.

In 2007, Dutschke failed in his bid as a Republican to defeat Democratic state representative Steve Holland, whose mother, a judge, received one of the ricin-tainted letters.

"We just want to move on," Holland told CNN, adding that he wanted justice for his mother.

"This could have been devastating. Mom could have died had this taken the worst-case scenario."

Dutschke also has said he has met Wicker.

Other charges

Dutschke, meanwhile, faces molestation charges in an unrelated case.

According to a grand jury indictment handed down this month and obtained by CNN, he is accused of molesting three girls under the age of 16. The accusations go back as far as 2007, according to the indictment.

Dutschke has repeatedly denied the charges in interviews with local media, and he pleaded innocent in court this month.

He closed his taekwondo studio after the allegations were made public.